Ink jet printing is a conventional technique by which printing is normally accomplished without contact between the printing apparatus and the medium on which the desired print characters are deposited. Such printing is accomplished by ejecting ink from an ink jet printhead of the printing apparatus via numerous methods which employ, for example, pressurized nozzles, electrostatic fields, piezo-electric elements and/or heaters for vapor phase bubble formation.
The ink compositions used in ink jet printing typically employ water, colorants and low molecular weight water miscible solvents. The colorants which may be employed include dyes or pigments. Pigments are often preferred and they are generally characterized as colorants that are not soluble in the liquid portion of the ink composition. Such ink compositions are, however, often deficient since print images prepared therefrom do not display wet-rub resistant properties. This means that print images made from such ink compositions typically smear when, for instance, the images are rubbed under pressure, wetted and/or subjected to commercially available highlighting or fluorescent markers.
It is of increasing interest to develop ink compositions that result in print images which resist such smearing. Moreover, it is of increasing interest to develop wet-rub resistant ink compositions that do not adversely interfere with parts of printing apparatuses. This invention, therefore, is directed to novel ink compositions which comprise binder materials, said novel ink compositions unexpectedly: result in print images which display wet-rub resistance; do not interfere with parts of printing apparatuses; display optical densities greater than about 1.18 (for black inks); and display good print quality (which is defined to mean substantially no print feathering or satellites).